A number of medical procedures involve or can be supplemented with the placement of an endoluminal prostheses, commonly referred to as a stent, that can be implanted in a lumen, such as a blood vessel or other natural pathway of a patient's body. Such stents typically define a generally tubular configuration, and are expandable from a relatively small diameter (low profile) to an enlarged diameter. While in its low profile configuration, the stent is advanced endoluminally, by a delivery device, through the body lumen to the site where the stent is to be placed. The stent then can be expanded to a larger diameter to firmly engage the inner wall of the body lumen. When the stent is delivered satisfactorily the delivery device is removed, leaving the implanted stent in place. In that manner, the stent may serve to maintain open a blood vessel or other natural duct, the functioning of which had become impaired as a result of a pathological or traumatic occurrence.
Among the medical procedures in which stents have had increasing use is in connection with percutaneous transluminal angioplasty (PTA), and particularly percutaneous transluminal coronary angioplasty (PTCA). PTA and PTCA involve the insertion and manipulation of a dilating catheter through the patient's arteries to place the dilatation balloon of the catheter within an obstructed portion (stenosis) of a blood vessel. The balloon is expanded forcibly within the obstruction to dilate that portion of the blood vessel, thereby restoring blood flow through the blood vessel. Among the more significant complications that may result from such angioplasty is when the dilated site becomes obstructed again, for example, by restenosis. By placing a stent within the blood vessel at the treated site, the tendency for such restenosis may be reduced.
Stenoses may often develop in the branching region of a patient's blood vessel. Treatment of a stenosis in the branched region may present numerous additional difficulties in the design of devices to dilate stenoses at the branched region. Techniques and devices have been developed to effect a dilatation at a branched region such as the "kissing balloon" technique described in U.S. Pat. No. 4,896,670, or pending Bard patent "Dual Balloon System." The need for an effective stent that can be placed at a bifurcated region has been recognized.